A DPF (Diesel Particulate Filter) is used on today’s diesel engines to remove harmful soot particles from entering the atmosphere.Like any filter it needs to be emptied from time to time, this is known as “passive regeneration”, where the soot is burned off at high temperature and leaves your vehicles exhaust as ash. The vehicles ECU normally takes care of this process as you drive(normally motorway driving) when the soot content inside the DPF reaches a set limit. The ECU must also see certain other parameters ie. vehicle temperature, speed,driving time and fuel level in order for regeneration to take place successfully.There are a number of factors that will prevent a passive regeneration from happening, constant city driving, DPF is full of soot, are a few At this point you may notice that your vehicle is down on power, different engine tone, DPF light illuminated. When this happens a forced regeneration may be required(after a system diagnostic is performed) this is where your vehicle is connect to a diagnostic tool and a regeneration is carried out. There are times however when even a forced regeneration is not effective ie. a totally blocked or melted DPF, at this point a new DPF will be required. There are companies offering to remove DPF filters and reprogrammed your vehicle ECU. It is an offence under the Road vehicles(construction and use) regulations to use a vehicle with a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet. Removal of the vehicles DPF will therefore make the vehicle illegal for road use, your insurance may also be null and void as the vehicle has been modified from manufacturers specifications. In the future NCT will be testing all diesel vehicles to ensure that DPF filters are intact, removal of a DPF will result in a FAIL on the emissions test. Don’t ignore a DPF warning light, it is possible you will do more engine damage resulting in a costly repair.